1. Field of the Invention
This invention relates to a shoe midsole and shoes using same by the use of an advanced material having high environmental adaptability obtained from biomass resources, which is a new ecological product of high technology and is different from conventional industrial materials.
2. Prior Art
Hide, soft or hard rubber and high molecular resins have been mainly used as a conventional shoe midsole, although each of these material confronts a problem respectively
Requirements of such a shoe sole are fastness, lightness, low wearability, resistance to temperatures, easy workability, low cost, etc.
There is no conventional material as described above which meets all of these requirements.
For example, hide is one of the best materials as a shoe midsole which looks high-grade, easily fits feet and is flexible, however, it tends to be affected by humidity and is not enough abrasion-resistant.
Soft or hard rubber is little affected by humidity although it does not look so high-grade, but is relatively heavy as a material, which is a problem for weight-saving.
On the other hand, a high molecular resin material is sufficiently flexible, little affected by humidity and appropriately abrasion-resistant, but does not look high-grade.
Accordingly, it is an object of the present invention to provide a shoe midsole and shoes using same in which disadvantages of conventional shoe midsole are overcome to yield a light in weight and long-life material of less sensitive to scratching, less influenceable to humidity, improved abrasion-resistance, air-permeability and workability.
According to the present invention, RB ceramics and CRB ceramics are used as a shoe midsole, which are very light in weight, hard and fast material of good abrasion-resistance, high moisture-absorbing properties and improved air-permeability. The RB and CRB ceramics are those materials prepared by the following method.
As is known, Kazuo Horikirigawa, the first inventor of the present invention has investigated and developed a porous carbon material by the use of rice bran (see, Kinou Zairyou Vol. 17, No. 5 pp. May 24 to 28, 1997). Rice bran is by-produced 900.000 ton/year in Japan or 33 million ton/year in the world.
The above mentioned literature describes a carbon material (hereinafter referred to as RB ceramics) and its method of preparation, in which a defatted product of rice bran and a thermosetting resin are mixed, kneaded and press-molded to form a molded material, followed by drying and baking the dried material in an atmosphere of inert gas.
According to the this method, degree of shrinkage between size of the press molded material and that of the material calcined in an inert gas reached almost 25%, which made it substantially difficult to form a precision molded material and finally has been improved by developing novel ceramics (hereinafter referred to as CRB ceramics).
CRB ceramics is an improved material of RB ceramics obtained from defatted rice bran and a thermosetting resin. CRB ceramics is a black resinous and porous ceramics prepared by mixing and kneading a defatted product of rice bran and a thermosetting resin and primarily baking a mixture thus obtained in an inert gas at 700 to 1,000xc2x0 C., followed by grinding to form carbonated powder of about 60 mesh or less, which is then mixed and kneaded with the thermosetting resin, press-molded at pressure of 20 Mp to 50 Mp and then heat-treated again in an atmosphere of inert gas at 100 to 1,100xc2x0 C. The most distinguished point of these two kinds of ceramics is that degree of shrinkage between size of the molded RB ceramics and that of the final product is almost 25%, while the degree is as advantageously small as 3% or less in the case of CRB ceramics.